However, police declared the gathering illegal shortly after it started under the controversial Montreal public order bylaw P-6. The bylaw makes it illegal to participate in an assembly with a face obscured by a scarf, hood or mask, and requires protesters to disclose to police in advance the location and itinerary of their demonstration.

Police said they issued a dispersal order, and also confirmed criminal acts, which consisted mainly of wielding sticks and throwing billiard balls at officers, were performed.

“It was getting dangerous for peace and safety and the public order,” said police Sgt. Jean-Bruno Latour.

Dozens of demonstrators tried to make their way to the march’s destination, a private club known by its street number, 357c.

Witnesses at Quebec’s inquiry into corruption in the construction industry have referred to the club in testimony as a meeting place for entrepreneurs, high-level bureaucrats and politicians to discuss business.

However, the demonstrators never reached the club.

Hundreds of police encircled the protesters at the intersection of de la Commune Street and St-Sulpice Street. They began herding — and in some cases, physically carrying — those detained into awaiting buses.

By 8 p.m., the police had wrapped up their operation.

The CLAC denounced the police intervention, saying they used disproportionate force against protesters.